Dc and low frequency noise analysis of hot-carrier induced degradation of low complexity 0.13 μm CMOS bipolar transistors

Low-frequency noise in downscaled silicon transistors: Trends, theory and practice

“…However, at higher biasing, the injection current dominates, and the intrinsic (Hooge) noise in the emitter resistance or injection current takes over the GR noise, resulting in a linear (or nearly) dependence S I C ∝I C and eventually a decrease of normalized noise S norm =S I C /I C 2 can be observed at high bias of BJT. Such cross-over between the noise sources in BJT is reported in [21], for example, when the base current was varied over 2-3 decades, and the cross-over causes a bias-dependent variation for K F , as illustrated earlier in Figure 2 with the solid diamonds labeled as "S I B ∝I B 1.2 ". A portion of these data is presented later in Figure 6 as function of the base DC current.…”

“…The areal dependence with increasing normalized noise in npn BJTs with smaller emitter area A E is shown in Figure 2, using the SPICE parameter K F defined from The data for more than 150 devices are collected from [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27], and shown in Figure 2 with some points omitted for clarity. Since the numbers spread over several decades, we use geometric averaging technique [28] to extract the trend in the data from the product A E ×K F ; and the trend is A E ×K F ≈5.6×10 -9 µm 2 with logarithmic standard deviation of σ dB =3.4dB.…”

“…The second factor for deviation of noise level around the trend in Figure 2 can be attributed to differences in the fabrication of BJT. The impact of several technology steps on the low-frequency noise in polysilicon emitter BJTs was reviewed several times, for example in [31], and extensively analyzed in the past [18,19,20,21,32,33,34,35,36,37,38,39,40]. From these studies, it is found that among the many sources that can contribute to the low-frequency noise, such as fluctuation in diffusion, surface recombination and charge trapping, the major noise source is associated with or located in the interfacial oxide (IFO) between poly and monosilicon layers in the emitter of BJT.…”

“…Typical types of cross-over in the noise in BJT are between areal and peripheral noise sources in the emitter region [14,21,35,36,42,60], noise from tunneling through IFO and series resistances (carrier number fluctuation, or coupled noise to the injection process, precisely) and diffusion noise (mobility fluctuation, or intrinsic noise of the current flow in emitter and base regions) [10,19,21,32,42,61,62], surface and bulk noise sources [14,21,24,36,37,42,60], and for very small-area BJTs (A E ≤0.1µm 2 ), the extension length of the base to the contact via becomes an issue for the low-frequency noise [36,37], since that extension is with large area compared to A E , and it is vulnerable to the surface noise from the oxide on the top of the structure. Also, in small-area BJTs, the crossover between generation-recombination (GR), random telegraph signal (RTS) and 1/f noise becomes apparent [11,12,17,18,30,35,63].…”

“…This effect is observed several times when the BJT was stressed electrically or after proton irradiation, and the generation-recombination currents are increased. An example from [21] is shown in Figure 6. Before stress, circles in Figure 6, a slope close S I B ∝(I B ) is observed, indicating low level of coupled noise owing to screening of surface noise from emitter-base junction, achieved by a high doping concentration at the surface of the base, using superficial base doping (SBD).…”